1. Field of the Invention
This invention relates to a process and apparatus for sealing seams in fabrics, such as protective barrier fabrics found in waterproof garments and the like, to preserve the imperviousness of such fabrics at the seamed joints thereof, at which joints intersecting panels or sections of fabric are joined together, such as by stitching, gluing or welding. The stitching (or poor gluing or welding) creates holes and/or gaps through the garments at such joints, which holes or gaps must be sealed if the integrity of the garment as a fluid barrier throughout its construction is to be maintained.
2. Description of Related Art
Sealing of seams in protective garments and the like, at the stitched joints where intersecting panels of cloth are joined together, is known. At such stitched joints, the respective fabric panels are generally not overlapping, but are butted together to form an extension extending substantially perpendicularly from the plane of the fabric panels, with the stitches at the base thereof. This extension is termed the “seam allowance”.
Typically a tape of material, which may or may not be of the same material as the protective barrier fabric, is affixed to the garment overlaying and sealing the seam(s) along each joint of the garment. Tapes may be thermoplastic materials, with sealing over a joint effected by thermal means such as a hot air gun which softens/melts the tape to a tacky state and seals the joint upon application. In addition, backing tapes having adhesives applied thereto are also employed. Known adhesives include thermoplastic and hot-melt urethane adhesives, certain glues, and, more recently, silicone adhesives have been disclosed which are suitable for this purpose.
Protective items which employ seam seals include waterproof garments such as rainwear and tents for outdoor activities. Operating room gowns are sealed to protect the wearer from blood borne pathogens and other body fluids. Firemen's coats must offer complete protection from a variety of possible penetrants, including water, pathogens and a wide range of various chemicals which could be encountered in any given fire emergency situation.
Seam seals also often must withstand hostile environmental conditions. For example, firefighters' turnout gear, including the seams, must withstand high temperatures without melting. In seams in surgical protective garments, it is desirable that the seals be autoclave-sterilized numerous times, while retaining their barrier properties.
Generally, protective garments can be made to include a special protective barrier layer and other coverings or carrier layers, such as backings or facing fabrics. In these garments, the protective barrier layer protects the wearer from a threat to well being, such as rain, snow, chemicals, viruses or blood pathogens. Examples of such barrier layers include microporous polytetrafluoroethylene membranes, microporous or monolithic polyurethane membranes, and polyetherpolyester membranes. The protective barrier layers may be attached to or laminated to one or more layers of an abrasion resistant, high strength backing, usually a woven or knit fabric layer, to form a composite protective barrier fabric. Nylon and polyester are examples of backing fabrics used in these constructions.
Garments may be assembled from these fabrics by sewing panels of the protective barrier fabric into the desired garment shape. Joints between the panels and other disruptions of the barrier layer must be sealed to provide a barrier which functions comparably to the protective barrier fabric itself. This generally is accomplished by applying a sealing tape over the seam, as discussed above.
The process of seam sealing of protective barrier garments generally includes consolidating the sealing tape over the joint in a consolidation nip. The nip may include opposing rollers.
U.S. Pat. No. 6,032,714 and the references cited therein disclose various processes and apparatus used in seam sealing, and are illustrative of the present state of this art. In known seam sealing techniques, it is difficult to lay the sealing tape onto the seamed joint such that the seam lies precisely along the centerline of the tape. As the seam allowance folds over during passage through the consolidation nip, it can interfere with the delicate application of the tape to the joint. An unguided seam allowance can flip-flop along the joint, overlapping the joint on one side of the seam and then the other, resulting in a wandering of the seam itself with respect to the centerline of the applied sealing tape, and vice versa. Top stitching, gluing or welding the seam allowance to one side before seam sealing can prevent this flip-flop. However, as seam tapes become narrower, the seam allowance also becomes narrower, making top stitching more difficult and more time consuming. For narrower seam tapes, it is desirable to keep the seam allowance (either top stitched or not top stitched) centered along the center of the seam sealing tape.
In contrast to the known prior art, the present invention provides a process and apparatus for guiding the seam allowance of a seamed joint in a fabric into alignment longitudinally with a seam sealing tape applied to the seam. The result is a sealed, seamed joint such that the seam is aligned longitudinally with the sealing tape.